The present invention relates to the control on a disk array, and particularly to a system for copying stored data in a disk unit into a spare disk when the disk unit constituting the disk array is closed or when the error frequency detected in the disk unit exceeds a given threshold.
The spare disk is disclosed in, for example, the invention of JP-A-7-210333. According to this gazette, when data in a disk unit where error occurs a certain number of times over a predetermined threshold and is detected, or data in a broken-down and closed disk unit, is reproduced into or copied into a spare disk, it is required that the data in the closed or error-detected disk be once read and written in a control unit, and then read from the control unit and stored in the spare disk, because the control unit manages the reproduction/copy operation.
Therefore, when this processing begins, the resources such as a microprocessor or a memory provided on the control unit are used for the reading and writing operations, resulting in lack of resources to be assigned to the read/write processing that is performed at the same time on the basis of the request from a host computer. Thus, the read/write performance of the disk array is reduced. In addition, it took a longer time to write data into the spare disk.
When a disk unit constituting a disk array is closed or when the error frequency detected in the disk unit exceeds a given threshold, the data stored in the disk unit must be reproduced or copied into the spare disk.
These arithmetic reproduction processing and copying processing are required to be performed in parallel with the read/write processing based on the request from the host computer to the control unit. However, since the resources such as a microprocessor or a memory provided on the control unit are used for this copying processing, a small number of resources are assigned to the read/write processing that needs to be performed at the same time. Thus, the read/write performance of the disk array deteriorates.
It is an object of the present invention to provide a disk array with its read/write performance improved by decreasing the number of resources of the control unit used for these processing operations (as for data transfer, no resource will be used), and make use of such resources effectively for the read/write processing based on the request from the host computer.